Won’t start sometimes and will randomly shut down engine
 

I recently bought a 2008 ranger, 2.3 4x2 auto. I know little to nothing about mechanical aspects of the truck, and lately I have been having some issues with it.

The main issues I have been having is the the truck will randomly not start. The engine will turnover very inconsistently. I took it to the dealership to have them check it out, and they still haven’t given me any response because they haven’t been able to replicate it. It doesn’t send out codes, and its not spark plugs or the fuel filter (had both changed recently).

Furthermore, the other day, while driving the truck, the engine shut off randomly without any warnings or lights going off. One of the times, was maybe 100ft after starting to drive it, and the other was while driving on the highway at 70mph.

At this point, I would just like to know what the issue might be, my main theories are fuel pump or the ECM, but like I said, I have no mechanical knowledge at all. So, what do you guys think?

Welcome to the forum

CEL(check engine light) is an important light

It should come on with Key on, that means computer(ECM) has powered up and is waiting for engine start up, no CEL = no computer
If CEL is on then when you start cranking the engine over the CEL should go OFF as soon as engine is spinning, this means the computer is getting a good Crank Sensor signal for Timing and will start spark and then fuel injectors
If CEL stays on then no start, because there is no spark and no fuel

There is no connection between starter motor and computer, only way computer will start spark and fuel is if it gets a good timing signal from spinning engine/crank

There is no sensor that can stall a running engine, except the Crank sensor failing but they don't recover from that, and it would set a code

Computer losing power could shut off running engine, and No CEL after engine was at 0 rpms, because computer is off, but all the other dash lights would OK

The computer is powered by a separate fuse and relay in engine bay fuse box, no connection to other systems or lights
So power could be cut to computer and only stall the engine no other visible effects

so if the CEL dont turn on, and there are no visible signs from it, its likely to be a computer shutting off issue?

thanks for the quick response, its really appreciated

Yes, if you are driving and engine stalls the CEL should come on as soon as engine is at 0rpms, even if still rolling, if it doesn't then computer lost power, its OFF, usually not a computer issue, its a power TO computer issue

If you turn on the key to start engine, CEL should come on, if it doesn't then computer is OFF and no start

Computer's can fail, just not that common, they are not like "computers" we are used to, they are calculator/computers, they just calculate fuel mixes on the fly, they last 40+ years so not at all like Our "regular" computers, lol, lucky to get 5 years

So in troubleshooting the computer is the very very last thing on the list

"Replaced ECM, no change" is often seen in troubleshooting threads

I see I see, so I most likely need to fix a power to computer then? Is that a simple fix?

Maybe, maybe not
Go here and get your 2008 Owners manual in PDF form: https://www.ranger-forums.com/genera...1-models-3747/

You need to look at the engine fuse box lay out
There will be a PCM(computer) fuse, and a PCM relay in that fuse box

PCM fuse wouldn't "fix itself" if it blew, but it connectors can get corroded, pull it out and have a look at the fuse and its slots

PCM relay can get a bad connection as well, pull it out and have a look, you can just replace this relay, they are not expensive

You can also look at the upper center of firewall and see the PCMs 3 connectors
If problem reoccurs you should pull off there 3 connectors and look for corrosion, clean and put them back on
The removal and reinstall of these 3 connectors CLEANS all the pins and slots

This is ASSUMING the computer is losing its power while running vehicle, so that needs to be confirmed first

Fuel pump can be shutting off as well, won't set a code just won't run

so the PCM relays are all intact, I talked to my girlfriend’s step father (who is a fellow ranger owner) and explained the situation, and he said it might be the fuel pump wiring. Is that something that sounds plausible in y’alls opinion?

Yes, if fuel pump is shutting off engine will also

The Fuel pump's 12v power is monitored by the computer, so if the 12v was shutting off the computer would set a code for that, unless the 12v was being cut off AT the gas tank connection, on top of the tank

Computer has these 4 codes to use
P0230 Fuel Pump Primary Circuit Malfunction >>> primary circuit is the fuel pump relay in the engine fuse box, with key on computer should see 12v here, as it travels thru the relay's coil and back to computer, not fuel pump 12v, relay's 12v

Secondary circuit is the 12volts going out from relay to the fuel pump, its measured at Inertia switch in the cab
P0231 Fuel Pump Secondary Circuit Low >>> low or no voltage after computer activates fuel pump relay
P0232 Fuel Pump Secondary Circuit High >>> has voltage BEFORE computer activates fuel pump relay
P0233 Fuel Pump Secondary Circuit Intermittent >>> the 12v is coming and going, bad connection or failing fuel pump relay

So if computer is not shutting off then it would set one of these codes if fuel pump was losing power while engine was running, unless, as said, it was a bad connection at the fuel pump on the top of the gas tank, or the fuel pump itself was failing